What can we tell about a country, culture, religion or fictional world from the dress codes that they impose? In the fictional world of Westeros, in ancient Rome and even today, clothing was tied to stereotypes.
As any fashion designer will tell you, a lot of unspoken words are whispered to an audience regarding a character's identity just from the clothing they wear on screen. For its first five seasons, Michele Clapton was lead costume designer for Game of Thrones. Last year, she told The Telegraph that during each of these seasons, Daenerys Targaryen has always worn a hidden pair of pants and boots underneath her dress. As Clapton notes, "There's always a fear in her that she will have to leave so it gives her the freedom to always escape and run. If she had silly shoes on she'd lose all her strength."
Quite right. Clapton's functional fashion choice is certainly a step up from Bryce Dallas Howard's insistence on running in high heels to escape dinosaurs in Jurassic World. Her layering of a dress over pants also represents the two worlds that Daenerys has straddled in the series: the world of a noble in a refined court and that of the invading general leading her troops.
In Rome of the late fourth century CE, pants were similarly controversial indicators of the blurring lines between civil society and warfare. This was due in large part to the fact that pants (called in Latin 'bracae') were seen as identifying items of clothing for groups perceived as "barbaric" or non-Roman. A number of these men had come to make up a significant portion of the Roman army by this date. Many Germanic groups, Goths and Huns were often characterized by historians of the time as wearing pants and boots. A law from 397 and then another in 399 CE strictly regulated the wearing of pants and boots in the city:
In addition to voicing a displeasure for certain items of clothing that appear to be coming into vogue, this law may have been signaling that the city of Rome was still seen as a safe haven from combat and thus off limits to martial attire. As I have written about before, the city of Rome was intended as a zone protected from weapons by a sacred boundary line called the pomerium. Even into the early Christian period, the city was cast as ideally off limits to most soldiers.
The laws of the late fourth century didn't seem to stop the barbarian fashion craze. In 416, another law was passed stipulating that those who wore skins and had long hair were similarly banned from coming within the walls of the city. This likely meant that within the confines of the Aurelian Walls, individuals were expected to adopt a traditional Roman urban dress (e.g., the toga worn by elite men) rather than attire associated with the "other." We can perhaps read fear into the dress code law of 416 in particular; it came just 6 years after the sack of the city of Rome by Alaric and his Goths.
It seems that Games of Thrones has also picked up on the imagined dichotomy between Rome and the "barbarian" seen within these dress codes. The presentation of the Wildlings in particular certainly appears to draw heavily from a description in Ammianus Marcellinus of the Huns' use of field mice as pelts for their clothing:
One way that the costume designers on the show denote that the Wildlings that lived beyond the wall are uncivilized people who are characteristically different from those living south of the wall is by similarly draping the Wildlings in skins and animal pelts. Notably, this is also just functional fashion. Animal skins are a lot warmer than silk or linen.